Question 51. The layer of the atmosphere which reflec ts the radiowaves back to the earth is called________
Answer: ionosphere
Question 52. Why does radio reception improve slightly during the night?
Answer: Sunlight affects radio broadcasts to some extent during the day
Question 53. Television signals cannot be received ordinarily beyond a particular distance due to________
Answer: curvature of the earth
Question 54. Planets are________
Answer: non-luminous bodies that do not twinkle
Question 55. A small hole in the window of a closed room forms an inverted image of outside building on the opposite wall of the room. This happens because________
Answer: of the rectilinear propagation of light
Question 56. ________part of the sun is visible during total solar eclipse.
Answer: corona
Question 57. The minimum length of a plane mirror in which a person can see himself full-length should be________
Answer: nearly half his height
Question 58. If you walk towards a plane mirror at a speed of 10 cm/ s, at what speed does your image approach you?
Answer: 20 cm/s
Question 59. If you stand in a room, where two adjacent walls are covered with plane mirrors, the total number of your images formed will be________
Answer: infinite
Question 60. ________type of mirror can be used to obtain the real image of an object.
Answer: concave mirror
Question 61. A dentist’s mirror is a________
Answer: concave mirror
Question 62. The type of mirror used in the head-lamps of cars is the________
Answer: parabolic concave mirror
Question 63. When a pencil is partly immersed in water in a slanting position, the immersed portion appears________
Answer: bent towards the water surface
Question 64. The sun remains visible for some time after it actually sets below the horizon. This happens due to________
Answer: atmospheric refraction
Question 65. If there were no atmosphere, the length of the day would________
Answer: decrease
Question 66. The sun and moon appear elliptical near the horizon due to________
Answer: refraction
Question 67. The twinkling of stars can be partly attributed to________
Answer: atmospheric refraction
Question 68. Planets do not twinkle because________
Answer: they are nearer to us and therefore minor variations in their intensity are not noticeable.
Question 69. A rainbow is formed by the________of light by water droplets.
Answer: dispersion and total internal reflection
Question 70. When white light passes through a glass prism, it gets dispersed into colours because________
Answer: different colours have different speeds in glass
Question 71. The three primary colours are________
Answer: blue, green and red
Question 72. When a person enters a dark room from bright light, he is not able to see clearly for a little while because the________
Answer: iris is unable to dilate the pupil immediately
Question 73. In old age, people have to wear spectacles for reading and writing because________
Answer: they lose the power of accommodation
Question 74. The sky appears blue because________
Answer: the atmosphere scatters blue colours more than the others
Question 75. In upper space, astronauts________see stars during the day.
Answer: can
Question 76. The sun appears deep orange-red before it sets because________
Answer: its light has to traverse, a thicker atmosphere, therefore, other colours get scattered and do not reach us
Question 77. Soap bubbles show multiple colours when viewed in white light because of________
Answer: the interference of the reflected light
Question 78. The technique of recording and reproducing three-dimensional images of objects is known as________
Answer: holography
Question 79. When a wave goes from one place to another, it transports________
Answer: energy
Question 80. The pitch (or shrillness) of a sound is determined by its________
Answer: frequency
Question 81. A woman’s voice is shriller than a man’s due to________
Answer: higher frequency
Question 82. The loudness of a sou nd wave is determi ned by its________
Answer: amplitude
Question 83. Sounds cannot travel through________
Answer: vacuum
Question 84. Thunder is heard much after a flash of lightning is seen because________
Answer: light travels much faster than sound
Question 85. Mach number is used in connection with the speed of________
Answer: aircraft
Question 86. A clearly separate echo of a sound is heard when the minimum distance of the reflecting surface from the source of sound is________
Answer: 17 m
Question 87. The walls and ceiling of an auditorium are covered with fibrous material, such as glass fibre, to________
Answer: absorb sound and prevent echoes
Question 88. A police van sounding its siren is moving away from an observer. The pitch (shrillness) of the sound from the siren relative to its normal pitch is________
Answer: lower
Question 89. A device used for measuring the depth of the sea is called________
Answer: fathometer
Question 90. If a bar magnet, tied in the middle with a thread, were suspended at the north pole of the earth, it would take________
Answer: a nearly vertical position with its north pole pointing downward
Question 91. The crackling sound, heard when dry hair is combed with a hard rubber comb, is due to________
Answer: small electric sparks
Question 92. A capacitor (condenser) is used in an electrical circuit to________
Answer: store electric charge
Question 93. ‘IC chips’ for computers are usually made of________
Answer: silicon
Question 94. Nichrome wire is used as a heating element in many appliances because________
Answer: it has high resistivity and it resists oxidation in air when red hot
Question 95. The starting current of an electric motor is________the current flowing after the motor reaches its normal running speed.
Answer: much greater than
Question 96. Energy conversions in a loudspeaker are________
Answer: electrical to mechanical to sound
Question 97. Ener gy conversion s takin g plac e in a microphone are________
Answer: sound to mechanical to electrical
Question 98. A transformer is a device for________
Answer: stepping up (or down) ac voltage
Question 99. In our houses we get 220 V ac . The value 220 represents________voltage.
Answer: effective
Question 100. The advantage of ac over dc is that________it can be transmitted over long distances with________loss.
Answer: minimum power
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1. What is the study of general science? |
2. Why is general science important? |
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